1. Field of Invention
This invention relates to a computer-controlled oil drilling rig, or derrick and in particular, to a block position and speed transducer therefor.
2. Description of the Prior Art
The physical structures utilized in the generation of a hydrocarbon producing well are known in the art. For example, drawworks have been long utilized in oil drilling rigs, or derricks, to raise or lower pipe stands and drill string into and out of the bore. Tongs are well known for making and breaking joints between pipe stands and the drill string. U.S. Pat. No. 3,881,375, issued to Robert R. Kelly and assigned to the assignee of the present invention, generally relates to a tongs. Racker arrangements for moving pipe stands from a storage location on a "set back" to an operating location within the derrick are also well-known. U.S. Pat. No. 3,501,017, issued to Noal E. Johnson et al. and U.S. Pat. No. 3,561,811, issued to John W. Turner, Jr., both relate generally to well pipe rackers and are both assigned to the assignee of the present invention.
Usually each of the broad functions performed by the mentioned structural systems requires the superintendence of many skilled derrick operators. Further, the work is often inefficiently performed, adding to the overall cost of the well. Yet further, even if the work is periodically efficient, it is difficult to maintain peak operating levels whereby each operation of the associated structures mesh so as to maintain the task of making-up or breaking-out a drill string at a minimum from a time standpoint consistent with safety of the personnel and the bore.
It is therefore advantageous to provide each of those structural systems with an appropriate electronic control system and to utilize a programmed general purpose digital computer to superintend and sequence the proper operation of the physical structures to most efficiently control derrick operations. It is appreciated that the elimination of manual control increases the efficiency and lowers the cost of well drilling operations.
By way of particular examples, in the prior art, the lifting or hoisting of the traveling block and elevator is done by the manual control of the electric motor drive on the derrick. The lowering motion of the traveling block is normally manually controlled by a drum brake. The lowering motion of a loaded traveling block (having a drill string thereon) is done by the manual control of the drum brake and uses an auxiliary brake to absorb the potential energy of the string during lowering. The manual control of these functions may be inefficient during foul weather or otherwise detrimental environments. It would be advantageous to provide an electronic control system in cooperative association with a programmed digital computer to control the lifting and lowering cycles, and specifically the velocity and position of the traveling block and elevator.
The loading on the traveling block and elevator, and specifically the increase in block loading when in the break-out cycle occassioned by friction in the bore as well as the decrease in block loading in the make-up cycle occassioned by an obstruction in the bore, present problems in the manual control of the derrick. It is therefore advantageous to provide an electronic load sensing arrangement to provide inputs to an electronic drawworks control to adjust the velocity and position of the traveling block in response thereto and to recognize potential dangerous loading conditions on the block.
The tongs are, as is known in the art, a hydraulically powered arrangement capable of making and breaking joints in a drill string. It is advantageous to provide an electronic network controlling the operations of the tongs, and to interconnect that control network with a programmed general purpose digital computer so as to repeatedly and efficiently operate the tongs to perform its function. Of course, since various of the physical structures discussed are actuated by hydraulic or pneumatic operators, suitable electro-hydraulic or electro-pneumatic interfaces must be provided. It is also advantageous to provide a sensor arrangement to locate the backup and power driven tong in vertical symmetry with respect to a horizontal plane passing through the tool joint.